There are a couple of ways:
One is to use iPhoto itself. But note that iPhoto manages the photos on Flickr. So if, for instance, you delete something in iPhoto it will also be deleted from Flickr.
You can use Flickr's own uploader or a 3rd party one, there are several. http://connectedflow.com/flickrexport/ has one such, there are others, and they have different features.
Yes, Flickr supports Exif, for precise details of exactly what is supported best to ask on a Flckr forum.
Given the price, I think Flickr is an excellent option. Smugmug is also an excellent service and well worth considering - and not too expensive.